Cyclic system for the manufacture of cuproammonium rayon and for the recovery of chemicals



Feb. 27 194'. w. H. FURNESS 2,370,156

CYCLIC SYSTEM FOR THE MANUFACTURE OF CUPROAMMONIUM RAYON AND FOR THE RECOVERY OF CHEMICALS Filed May 1, 1940 Q 29% EB? .5: all x h N a INVENTOR ATTORNEYS.

20:54am e q Exam OFWJ Patented Feb. 27, 1945 CYCLIC SYSTEM FOR THE MANUFACTURE OF CUPROAMMONIUM RAYON AND FOR THE RECOVERY OF CHEMICALS William H. Fumess, Haddonfield, N. J., assignor to American Rayon Company, Inc.,

River-ton,

N. J.. a corporation of New Jersey Application May 1, 1940, Serial No. 332,694

9'Claims.

This invention relates to the manufacture of rayon, films and like cellulose products, from cuprammonium cellulose solutions, and it is directed to a cyclic system for recovering chemicals employed, which is simple in nature and very effective from the standpoint of economy.

The system is diagrammatically illustrated in the accompanying drawing on one form of apparatus suitable for the purposes of the invention.

In carrying out my invention, for example, in the manufacture of rayon, the cellulosic spinning solution, preferably prepared as hereinafter indicated, is spun through suitable spinnerets l, into a circulating dilute caustic soda setting bath 2, desirably containing from about 25 to about 45 grams per liter of NaOH and possibly more, depending upon such factors as the concentration of the cellulose in the solution being spun.

From the setting bath, the bundle of filaments is continuously led by means of suitable guides (not shown) to a suitable device, preferably a revolving cage'3, which operates to advance the bundle continuously in the form of a helix and from which the finished yarn is ultimately led for winding on suitable holders.

On the cage, the freshly spun filaments are treated, the first treatment given being a. hot water wash; the second, a dilute sulphuric acid wash; the third a water wash or washes; and th fourth (which is optional and may be carried out elsewhere) a drying. In order to conveniently and separately collect the hot water wash liquor and the acid wash liquor and for other reasons, these two stages are separated, as for example, by leading the bundle of filaments, after leaving the hot water wash section, from oil the cage, over a roll 4 and back to the cage. (If desired two cages instead of one cage or other suitable apparatus. may be employed for this purpose.)

In and on the freshly spun filaments leaving the setting bath 2, are caustic soda, copper and ammonia. The hot water washing treatment removes the bulk of the caustic soda and, for all practical purposes, all of th ammonia, part of the ammonia being removed by evaporation in the form of gas and part being washed away by the water. A substantial portion of the copper is likewise removed from the filaments, probably in the form of cupric hydroxide. This cuprlc hydroxide is most likely present in the filaments largely in solution. The water apparently dilutes the ammonia and in consequence of this and of the evaporation of some of the ammonia as gas, the cupric hydroxide can no longer remain in solution but comes out and is washed away with the ammonia and is found in the wash liquor, collecting in a suitable pan 5, located below the hot water wash.

This removal of the bulk of the caustic soda, or

practically all of the ammonia, and of a substantial portion of the copper from the filaments, preliminary to the sulphuric acid treatment, has a number of important advantages. In the first place, it reduces the amount of acid required. (If

these were removed solely by the acid wash, a much greater quantity of acid would be required.)

The removal of the bulk of the caustic soda by the hot water wash has the followirg additional advantages. This makes it possible to recover the caustic soda as such and reuse it by returning it to the setting bath system, as will later be described. This effects a great economy. Where caustic soda is solely removed from the filaments by the acid wash, it is removed by the reaction, of sulphuric acid therewith to form sodium sulphate, the wash solutions being so dilute that the cost of recovery of the caustic soda from the sodium sulphate is so great as to be prohibitive, in 'consequence of which the sodium sulphate liquors are ordinarily discarded. Furthermore, by my process, the amount of caustic soda carried over into the acid section is so small that the sodium sulphate may be left in the liquors being re-used in the system, and removed from time to time, if desired, as hereinafter to be pointed out, and sold.

The additional advantages of removing a substantial part of the copper from the filaments befor the acid wash treatment are as follows. In the acid wash liquors, there is always some free or excess sulphuric acid, in addition to copper sulphate and sodium sulphate. For economy, the free or excess acid should be recovered, and one of the advantages of the removal of the copper as copper hydroxide in the hot water wash treatment is that this copper hydroxide, or a portion of it, may be used to neutralize the free acid, the product of the reaction being copper sulphate. This copper sulphate is recovered and re-used, as will hereinafter be described. The free acid is thereby recovered and used in the system.

The additional advantage of removing practically all of the ammonia from the filaments prior to the acid'wash treatment is that any appreciable amount of ammonia in the filaments being subjected to the acid wash, would result in the formation of ammonium sulphate, which, in appreciable quantities, would interfere with the method to be described by which I recover copper from the acid wash liquor. Furthermore,

ammonia being one of the chemicals employed, its recovery is of value.

Referring now to the acid wash treatment, a solution of sulphuric acid is applied to the filaments pursuant to the hot water wash in order to remove the remaining caustic soda and copper from the filaments. The products of the reaction are copper sulphate and sodium sulphate. These, along with acid, are largely washed out and are contained in the wash liquor from the acid section, for which purpose it is desirable to have the pipe or pipes 6, supplying water for the ensuing washing operation, overlap the acid section so that the water wash drippings from the overlapping portions will be collected along with the acid wash liquor, proper, which is delivered to the vessel 1 for the recovery of the copper sulphate.

By the time the filaments reach the water wash section proper, following the acid wash section, there is very little chemical in the filaments but even it may be recovered as hereinafter indicated.

Referring now to the circulating caustic soda setting bath, this is being constantly replenished from a storage tank 8 and is constantly overflowing, the overflow being ultimately returned, substantially free of copper and ammonia, to the storage tank for recirculation. Since the spinning solution being spun into the spinning bath is constantly carrying caustic soda, ammonia, sodium sulphate and copper into the setting bath, the setting bath has a tendency to build up in these chemicals, for which reason it is not only desirable to keep the bath circulating but also to recondition the bath by the removal of such chemicals in order to maintain most effective spinning conditions, particularly with the dilute caustic soda setting bath employed. It is further highly desirable to recover and re-use the caustic soda, copper and ammonia in the system. How this is done will now be described.

The overflow from the setting bath is ultimately pumped to a boiler 9 through the pipe l0, and from the boiler 9 the liquid, at substantially boiling temperature, is discharged into the closed pan l l which has a relatively extended area. By reason of the heating, the ammonia is driven off in the boiler and in the pan in the form of gas, along with some water vapor'or steam, and the copper in the overflow from the setting bath is converted into black copper oxide.

The liquor overflowing from the pan II is led to a settling tank or series of settling tanks l2, in which the black oxide has opportunity to settle out by sedimentation and from which it is withdrawn from time to time, washed free of caustic soda, in which condition it is ready for re-use in the system, as will hereinafter be described. (The black oxide may be otherwise separated, as by centrifuging, filtering and the like.)

Since the overflow has been freed of ammonia and copper, the liquor in the settling tanks I2 is a caustic soda solution of approximately the concentration of the setting bath. The caustic soda solution from the last settling tank, l2, substantially free of copper and ammonia, may thus be and is returned to the storage tank 8 for recirculation. For this purpose it should be cool, for which reason I pass the overflow from the pan II, on its way to the settling tanks l2, in heat interchanging relation with the overflow from the setting bath by means of the heat exchanger i3. By this'heat exchanger the overflow from the setting bath is preheated and the overflow from the pan II is brought down to about room temperature.

There is relatively little sodium sulphate in the returning caustic soda solution. It causes no difliculty and from time to time may, if desired. be crystallized out in whole or in part by cooling, centrifuged, purified and sold.

The steam and ammonia gas collecting in the pan ll above the liquor therein is piped off through a condenser-heat inter-changer it through which the overflow from the setting bath is passed in heat exchanging relation with the collected ammonia gas and steam. In consequence, the ammonia is condensed to form ammonia water and the overflow from the setting bath is preheated. This heat exchanger i4 is located in advance of the exchanger I3 so that the overflow from the setting bath is twice preheated, thus recovering a portion of the heat utilized in boiling the overflow from the setting bath.

The ammonia water formed in the condenser I4 may be utilized as hereinafter indicated, for

example in preparing fresh spinning solution or in the cop er sulphate recovery system.

Attention will now be directed to the wash liquors from the hot water wash section and the manner in which chemical is recovered therefrom and re-used in the system. The wash liquor from the hot water wash section contains caustic soda, ammonia, sodium sulphate, and cupric hydroxide, which for reasons hereinbefore pointed out, comes out of solution. The collected wash liquors are passed through a settling tank or a series of settling tanks IS in which the copper hydroxide has opportunity to settle and from which it is from time to time withdrawn, and washed free of caustic soda, in which condition it is ready for re-use in the system, as will appear. The liquor running off from the last settling tank l5 now contains caustic soda, sodium sulphate, and ammonia, together with a small amount of residual copper. In order to remove the ammonia and increase the concentration of the caustic soda in the liquor,

the liquor flowing from the last settlin tank is passed through a heater [6 in which the ammonia is driven off along with some water vapor. Likewise therein the residual copper, in whole or in part, is converted by the heat to the black copper oxide and is carried off with the liquor into a second heater i! where the liquor is boiled to increase the concentration of the caustic soda. Any residual copper remaining in the liquor is here converted into the insoluble black copper oxide, and the black copper oxide precipitates and is removed from time to time and washed free of caustic soda, when it is ready for re-use in the system.

Itis to be understood that the liquor from the heater i! may be discharged into a settling tank (not shown) if desired, to permit effective settling out of the copper oxide.

The spinning solution and the setting solution of course require a given amount of water respectively. The hot water wash however introduces water into the system. This additional water is evaporated in the boiler ll 50 that the concentration of the supernatant liquor in the boiler i1 is substantially that of the setting bath, so that the concentrated liquor may be directly returned to the storage tank 8 for the caustic soda setting solution and recirculated. (In this connection, it is to be observed that the caustic soda solution returning to the storage tank 8 does not introduce additional water into the system but is only returning water which is already necessarily present in the system. From time to time, it is necessary to add caustic soda to adjust the setting bath.)

Since there is already some sodium sulphate in the water used for the hot water wash (as will further appear), and since there is also some sodium sulphate in the filaments being subjected to the hot water wash, the hot water wash liquor contains sodium sulphate. Hence the concentrated caustic soda liquor leaving the boiler I! also contains sodium sulphate. The sodium sulphate,

however, is present in such quantity that it pre-' sents no difficulty. But since concentrated liquor leaving the boiler i! must be cooled before return to the caustic soda setting bath storage tank 8 it is convenient to pass it through the cooler IS on its way to the storage tank. In this cooler, the sodium sulphate is separated out by crystallization with the removal of some water. Thus the cooler l8 and the boiler ll between them remove substantially all of the water introduced into the system by the hot water wash. The crystallized sodium sulphate may be withdrawn from the cooler l8 from time to time and centrifuged, purified, and sold. (When the concentration of sodium sulphate in the setting bath becomes sufficiently high, it may be bypassed through the cooler and crystallized out in whole or in part.)

If for any other reason it is desired to do so, the cooler l8 may be by-passed. When the cooler I8 is thus by-passed, the concentrated solution returning from the boiler l l must be allowed to cool before re-use.

As thus far described, it will be seen that there is ammonia liberated as gas in the hot water wash section and in the heater H6. The ammonia gas from the hot water wash section is collected and delivered, along with much air, by the pipe Hi to an absorbent tower such as a cokefilled tower 2D to which a dilute solution of sulphuric acid is likewise introduced, the air escaping through the pipe 2i. During the trickin the system, as hereinbefore described, may also ling, ammonium sulphate is produced which is discharged into the vessel 22, where in due course it crystallizes out and is withdrawn from time to time.

The ammonia gas and steam collected from the vessel iii are led by the pipe 23 to the condenser 24 for discharge as ammonia water into the vessel 25a into which the ammonia water previously obtained in the system is led. To the ammonium sulphate removed from the vessel 22 is now added cupric hydroxide, the source of which is the cupric hydroxide recovered from the system as hereinbefore described, and ammonia water from the vessel 25a. The reaction is which iscopper tetrammonio sulphate, which is used for making spinning solution.

Considering now the acid wash section, the acid wash liquor contains copper sulphate, free sulphuric acid, and some sodium sulphate, and the liquor is collected and delivered to the vessel 1 as hereinbefore pointed out. The free sulphuric acid may be recovered for re-use in the system by using the black copper oxide recovered from the system as hereinbefore described, by adding the black copper oxide to the vessel 1, which will 7 with the aid of heat, react with the free sulphuric acid to form copper sulphate. Usually there will be insufficient black oxide to neutralize all of the free acid, so cupric hydroxide recovered to form copper sulphate. To remove the copper sulphate from the liquor (that which was already present and that formed by the neutralization of the free acid), I employ cupric hydroxide, the

reaction being to form basic copper sulphate which is insoluble and precipitates out in the vessel 1, from which it is withdrawn or otherwise separated. (In starting the system an initial amount of cupric hydroxide must be provided, but this body of cupric hydroxide is used over and over again, the needs of the system otherwise being supplied by the cupric hydroxide which is recovered in the process.) copper sulphate thus produced there is now added ammonia recovered from the system, 4 mols of NH: being added for each sulphuric acid radical present. The reaction results in the production of copper hydroxide and tetrammonio copper sulphate, the cupric hydroxide being -re-used as herein indicated, and the tetrammonio copper sulphate being employed in the manufacture of spinning solution.

The liquor from the vessel 1, freed of excess acid and copper sulphate as described, and containing sodium sulphate, is now led to a heater 25 where it is heated and is used as the hot water wash. From the hot water wash liquid the sodium sulphate may be removed, if desired, and as hereinbefore described.

The sulphuric acid introduced into the coke tower eventually comes out of the process in the form of sodium sulphate.

It will be seen that I have provided a simple, effective and economical system. The copper,

- ammonia and caustic soda are recovered for reuse in the system, some of them directly in the form in which they are used, and others in such form that when reacted, the reaction products are in the form in which they are directly used in the system. The water drawn off as steam from the heater I1 is condensed and may be used (purified if necessary) as the final wash water to remove the last traces of acid and soluble salts from the filaments. The wash water from this section containing these traces of acid and soluble copper salts may be utilized to dilute the'acid for the acid wash, and the final acid wash liquor, as hereinbefore described, may be used for the hot water wash. Thus for all practical purposes the same body of water may, if desired, be used over and over again in the hot water wash, the acid wash, and the final water wash sections. This represents an economy because it is rare that water is sufficiently pure and free from iron to permit of its use without purification, softening, etc. Thus even the traces of acid and copper in the final wash liquor may be recovered. Moreover, the condensing of steam may be brought about by passing the air used in drying in heat interchanging relation with the steam, whereby the air is preheated and heat is recovered.

It will be seen that copper is removed and recovered in the reconditioning of the setting bath merely by the application of heat and separation as by sedimentation; and that the ammonia in the setting bath overflow liquor is removed by heat and recovered by condensation. The caustic soda is returned in solution to the storage tank. Insofar as the prewater-wash section is concerned the copper is removed and recovered 'by dilution and separation or by sedimentation, the ammonia, by heating and condensation, and the To the basic caustic soda by dilution and re-concentration by heating. Insofar as the acid wash section is concerned the copper (in the form of copper sulphate) is recovered by reaction with chemicals obtained from the system which converts it into a form in which it is directly used.

The amount of sodium sulphate formed in the system is relatively small and this is recoverable as indicated. No chemicals are added to the system save the sulphuric acid introduced in the coke tower and the NaOH needed to convert it to sodium sulphate. The initial quantity of cupric hydroxide required, above referred to, is used over and over again.

To summarize, the spinning solution requires cellulose, caustic soda, copper and ammonia.

Practically all of the ammonia and copper are recovered and re-used in the system. A large part of the caustic soda is recovered in solution and utilized in the setting bath, the remaining caustic soda coming out of the system in the form of sodium sulphate. The acid used in the system likewise comes out of the system in this sodium sulphate, which is sold. It will thus be seen that the make-up chemical required is correspondingly small and that the cost of raw materials is very low.

While I have described the removal of the bulk of the caustic soda, etc., by the use of a hot water wash, the water employed need not be hot. I prefer hot water as I can accomplish the.

results with a smaller volume. The caustic soda is more soluble in hot than in cold water. The temperature of the water should not be so high as to convert the cupric hydroxide in the hotwater wash section to the black copper oxide because, since it is usable in the system as cupric hydroxide, it would only be wasteful to convert it to black copper oxide.

Since certain features of the above system are capable of and valuable for independent use, I am not herein claiming them separately but do so in copending applications.

As before stated, the cuprammonium cellulosic spinning solution may be prepared in any desired manner. I prefer to use wood pulp, in which case I proceed in accordance with my pending application Serial No. 129,820, filed March 9, 1937 (now Patent No. 2,225,431, dated December 17, 1940). In brief, the process is as follows:

In the preferred practice of my invention I take the sheets of wood pulp and, without pretreatment, and irrespective of its viscosity, dissolve them either in the sheet form or by tearing them up into pieces. say about four to six inches square.

Using the smaller squares for illustration, the following is typical of the preferred procedure and proportions. I take 486 grams of wood pulp in squares and immerse them in 1804 cc. of a solution containing 212 grams of NaOH, the squares preferably being immersed singly to be sure that they are thoroughly Wet. The wetted squares which have absorbed the 1804 cc. are now placed in a press and 731 cc. of the solution squeezed out. The squeezed material is now placed in an agitator such as a stirrer or shredder and is thereby riced, after which is added 5 pounds of cracked ice and 2 pounds of water preferably in that order. The riced material is churned until it makes a smooth slurry.

To the slurry is added 690 cc. of 26 B. ammonia and one pound of cracked ice, the churning being continued.

After this I add 3 liters of tetrammonlo copper sulphate containing 250 grams of 68 grams of NH3 and 5 pounds of cracked ice, churning being continued. The temperature lowers to about 0 C.

The mols of NH; are in excess of the theoretical 4 mols. The slurry is immediately affected by the tetrammonio copper sulphate, the latter removing combined caustic soda and forming in situ which I term the double salt of copper sulphate ammonia and caustic soda which is an extremely active solvent of cellulose. The tetrammonio copper sulphate quickly penetrates the pulp and this is expedited by the continued churning. Thus the dissolving action is very rapid and in about 20 minutes time the cellulose is completely in solution. No copper hydroxide is formed except as the salt of copper sulphate ammonia and caustic soda combines with the cellulose in the dissolving,

Some of the water is used in the form of ice as a simple means for providing the refrigeration needed. This of course may be otherwise furnished.

If cotton linters are used, then I prefer to proceed as described in my pending application Serial No. 305,928, filed November 24, 1939 (now Patent No. 2,247,124, dated June 24, 1941). In brief that process is as follows.

I prepare the solution preferably as follows: Dissolve 160.7 ounces of copper sulphate (CuSOa-i-SHzO) in 21.5 liters of water. Add 8 liters aqua ammonia (26 B.) and agitate until the basic copper sulphate first formed is redissolved. Cool the solution to about 15 C. Any iron which is present will quickly settle and may be easily removed. Pour into a mixer and add 12 lbs. of ice, preferably cracked.

Dissolve 52.5 ounces caustic soda (76% NazO) in 6 liters of water, cool to about 15 C.; and add 3 lbs. of cracked ice.

Stir each solution until the ice is nearly melted which will simultaneously cool and dilute, bringing the temperature of each to about 4 C. Pour the solutions together and agitate for about 30 seconds, which lowers the temperature below 0 C.

Although the refrigeration may be otherwise provided, the advantage of cooling with ice is that the cooling occurs at the point of dilution which prevents crystallization as the cooling occurs and secures rapid cooling in large volumes.

Then immediately add ounces of bleached cotton linters and mix. The solution of the cellulose, with such temperature, will be complete within about 20 minutes and a perfectly clear solution will be obtained substantially free from undissolved fiber and precipitated copper hydroxide.

It will be obvious that the process is applicable in whole and in part in the manufacture of Cellophane (and other cellulosic products) with such changes in physical manipulation or handling as are necessary by reason of the fact that the cellulose is spun in sheets rather than in filament form.

It will be apparent that within the general cycle herein described and now to be claimed, there are several novel subordinate features, some of which are separately useful. Reference may be had in this regard to three applications filed monia, the ammonia being removed as gas by f heat and bein recovered by condensation and the copper hydroxide being converted to oxide by heat, collected by sedimentation and removed, and the caustic soda liquor, freed of copper values and ammonia, being returned to the setting bath;

' removing from the freshly spun material a large portion of the caustic soda, the ammonia and a substantial part of the copper (present as hydroxide) therein by washing with Water, collecting the wash water and removing the copper hydroxide and ammonia therefrom, a part of the copper hydroxide being removed by sedimentation and separation and the remainder being removed by heat and collected by sedimentation and separated, and the ammonia being removed by heat and collected by condensation, the liquor being concentrated by heat and the concentrated liquor being returned to the setting bath; removing the remaining caustic soda and copper (present as hydroxide) from the freshly spun material by a sulphuric acid wash, collecting the acid wash liquor and removing copper sulphate and excess sulphuric acid therefrom; neutralizing the excess acid by additional copper values derived from the system by previously recited steps to form more copper sulphate, and converting the copper sulphate into basic copper sulphate by copper hydroxide derived from previously-recited steps of the process; and collecting the basic copper sulphate by sedimentation, treating it with ammonia derived from previously-recited steps of the process to form tetrammonium copper sulphate and cupric hydroxide and forming from the tetrammonium copper sulphate so produced and from fresh quantities of cellulosic material, additional amounts of cuproammonium cellulosic solution.

2. In the continuous manufacture of cuproammom'um rayon, films and the like, the process which comprises the steps of: spinning the cuproammonium cellulosic solution into a circulating caustic soda setting bath, heating the overflow from the setting bath to drive off ammonia and to cause copper (originally present as hydroxide) to come out of solution as copper oxide, separating the copper oxide from the liquor and returning the latter free of copper values and ammonia to the caustic soda setting bath; continuously removing with hot water from the freshly spun material after leaving the setting bath and while in a plastic condition, a large amount of the caustic soda, the ammonia, and a substantial part of the copper (present as hydroxide), collecting the water wash liquor, removing ammonia and copper hydroxide therefrom'and evaporating a substantial part of the water introduced by the hot water wash, and returning the thus concentrated liquor free of copper values and ammonia to the setting bath; thereafter continuously subjecting the material to a sulphuric acid wash to remove the remaining copper (present as hydroxide) and caustic soda, collecting the acid wash liquor, removing copper sulphate and free sulphuric acid therefrom, heating the remaining liquor and utilizing the same as the water wash liquid in the water washing hereinbefore referred to.

3. In the continuous manufacture of cuproammonium rayon, films and the like, the process which comprises the steps of: spinning the cuproammonium cellulosic solution into a circulating caustic soda bath, heating the overflow from the setting bath to drive on ammonia and to convert copper (originally present as hydroxide) to copper oxide, separating the copper oxide from the liquor and returning the latter free of copper values and ammonia to the caustic soda setting bath; and continuously removing with water from the freshly spun material after leaving the setting bath and while in a plastic condition, a

large amount of the caustic soda, the ammonia and a substantial part of the copper in the form of cupric hydroxide, collecting the water wash liquor, allowing the cupric hydroxide to settle for separation, removing the ammonia from the wash water liquor, and evaporating a substantial part of the water introduced by the water wash, and returning the thus concentrated liquor free of copper values and ammonia to the setting bath; thereafter continuously subjectin the material to a sulphuric acid wash to remove the remaining copper (present as hydroxide) and caustic soda, collecting the acid wash liquor, and removing copper sulphate and most of the free sulphuric acid therefrom; heating the remaining liquor of the acid wash, and using it in a heated condition in the water-wash first named for removing the caustic soda, ammonia, and copper values from the freshly spun filaments.

4. In the continuous manufacture of cuproammonium rayon, films and the like, the process which comprises the steps of: spinning the cuproammonium cellulosic solution into a circulating caustic soda setting bath, heating the overflow from the setting bath to drive off ammonia and to cause copper (originally present as hydroxide) to come out of solution as copper oxide, separating the copper oxide from the liquor and returning the latter free of copper values and ammonia to the caustic soda setting bath; continuously removing with water, from the freshly spun material after leaving the setting bath and while in a plastic condition, a large amount of the caustic soda, the ammonia, and a substantial part of the copper (present as hydroxide), collecting the water wash liquor, allowing the copper hydroxide to settle for removal, heating the liquor to drive ofi ammonia and to remove residual copper values therefrom as copper oxide, and evaporating a substantial part of the water introduced by the water wash, and returning the thus concentrated liquor free of copper values and ammom'a to the setting bath; thereafter continuously subjecting the material to a sulphuric acid wash to remove the remaining copper (present as hydroxide) and caustic soda therefrom, collecting the acid wash liquors, neutralizing the excess acid therein and converting the copper sulphate therein into basic copper sulphate, allowing the basic copper sulphate to settle and removing it, heating the remaining liquor and utilizing it as the water wash liquor for the water wash hereinbefore referred to.

5. In the continuous manufacture of cuproammonium rayon, films and the like, the process which comprises the steps of spinning the cuproammonium cellulosic solution into a. circulating caustic soda setting bath, heating the overflow from the setting bath to drive on ammonia and to cause copper (originally present as hydroxide) to come out of solution as copper oxide, separating the copper oxide from the liquor and returning the latter free of copper values and ammonia to the caustic soda setting bath; continuously removing with water, from the freshly spun material after leaving the setting bath and while in a plastic condition, a large amount of the caustic soda, the ammonia, and a substantial part of the copper (present as hydroxide), collecting the water wash liquor, allowing the copper hydroxide to settle for removal, heating the liquor to drive off ammonia and to remove residual copper values therefrom as copper oxide, and evaporating a substantial part of the water introduced by the water wash, and returning the thus concentrated liquor free of copper values and ammonia to the setting bath; thereafter continuously subjecting the material to a sulphuric acid wash to remove the remaining copper (present as hydroxide) and caustic soda therefrom, collecting the acid wash liquors, neutralizing the excess acid therein and converting the copper sulphate therein into basic copper sulphate, allowing the basic copper sulphate to settle and removing it, heating the remaining liquor and utilizing it as the water wash liquor for the water wash hereinbefore referred to; and washing the filaments to remove the acid and soluble salts; the last mentioned wash water being utilized in preparing the acid wash solution.

6. In the continuous manufacture of cuproammonium rayon, films and the like, the process which comprises the steps of: spinning the cuproammonium cellulosic solution into a circulating caustic soda bath, heating the overflow from the setting bath to drive off ammonia and to cause copper (originally present as hydroxide) to come out of solution as copper oxide, separating the copper oxide from the liquor, returning the liquor free of copper values and ammonia to the caustic soda setting bath, collecting the ammonia and water vapor driven off in the heating, and condensing the same to form ammonia water; continuously removing with water, from the freshly spun material after leaving the setting bath and while in a plastic condition, a large amount of the caustic soda, the ammonia and a substantial part of the copper (present as hydroxide), collecting the water wash liquor, allowing copper hydroxide to settle and removing the same, heating to remove ammonia, continuing the heating to evaporate a substantial portion of the water introduced by the water wash and to remove residual copper values as copper oxide, returning the thus concentrated liquor free of copper values and ammonia to the setting bath, and collecting the ammonia gas and water vapor driven off and condensing the same to ammonia water; thereafter continuously subjecting the material to a sulphuric acid wash to remove the remaining copper (present as hydroxide) and caustic soda, collecting the acid wash liquor, neutralizing the excess sulphuric acid therein with copper values derived from the system, converting copper sulphate therein into basic copper sulphate with cupric hydroxide derived from the system, allowing the basic copper sulphate to settle and removing the same, heating the remaining liquor and using it as the water wash liquid in the water wash hereinbefore referred to, collecting the ammonia gas evolved during the water wash and subjecting the same to sulphuric acid to form ammonium sulphate, removing the ammonium sulphate, adding thereto ammonia water derived from the system and cupric hydroxide also derived from the system to form tetrammonio copper sulphate; adding to the basic copper sulphate removed from the system, ammonia derived from the system to form tetrammonio copper sulphate and cupric hydroxide, allowing the cupric hydroxide to settle and separating it, utilizing the tetrammonio copper sulphate to form spinning solution and the cupric hydroxide to convert more copper sulphate into basic copper sulphate.

'7. In the continuous manufacture of cuproammonium rayon, films and the like, the process which comprises the steps of spinning the cuproammonium cellulosic solution into a circulatin caustic soda setting bath, heating the overflow from the setting bath to drive off ammonia and to cause copper (originally present as hydroxide) to come out of solution as copper oxide, separating the copper oxide from the liquor and returning the latter free of copper values and ammonia to the caustic soda setting bath; continuously removing with water in a first water wash, from the freshly spun material after leaving the said bath and while in a plastic condition, a large amount of the caustic soda, the ammonia and a substantial part of the copper hydroxide present therein, collecting the used liquor from the first water wash, allowing the copper hydroxide to settle therefrom for separation, removing ammonia from the liquor, evaporating a substantial part of the water, and returning the thus concentrated liquor free of copper values and ammonia to the setting bath, and condensing into water the steam thus evaporated; thereafter continuously subjecting the material to a dilute sulphuric acid wash; and washing with water in a second water wash to remove acid and soluble salts, and collecting the used wash water; the water condensed from the used liquor of the first water wash being used as the wash water of the second water wash and the collected used wash water from the second water wash being used to prepare the acid solution; and water recovered from the used liquor of the acid wash being utilized in said first water wash for said removal of caustic soda, copper values and ammonia from the freshly spun filaments.

8. In the continuous manufacture of cuproammonium rayon, films and th like, the process which comprises the steps of spinning the cuproammonium cellulosic solution into a circulating caustic soda bath, heating the overflow from the setting bath to drive off ammonia and to convert the copper therein to black copper oxide, allowing the black copper oxide to settle and separating it from the liquor, returning the liquor free of copper and ammonia to the caustic soda setting bath. collecting and condensing the ammonia gas and water vapor driven oiT into ammonia water, and utilizing the ammonia water in the system; continuously removing with a hot water wash, from the freshly spun material after leaving the setting bath and while in a plastic condition, a large amount of the caustic soda, the ammonia and a substantial part of the copper therein, collecting the wash liquor, allowing the cupric hydroxide therein to settle out and separating it, heating the liquor to drive off ammonia and further heating to evaporate the water introduced into the system by the water wash, as steam, and to convert residual copper into black copper oxide, allowing the black copper oxide to settle and separating it, and returning the liquor free of copper and ammonia to the caustic soda setting bath, collecting the ammonia gas and water vapor driven off therewith and condensing the same into ammonia water and utilizing it in the system; collecting the ammonia gas and water vapor driven oil by the hot water wash and reacting the same with sulphuric acid to form ammonium sulphate, and removing and reacting the ammonium sulphate with ammonia water and cupric hydroxide derived from the system to form tetrammonio copper sulphate, and utilizing the tetrammonio copper sulphate in preparing cellulosic spinning solution; subjecting the material to a sulphuric acid wash to remove the remaining copper and caustic soda therefrom, collecting the wash liquor, neutralizing the excess sulphuric acid therein with copper values derived from the system to form copper sulphate, converting the copper sulphate in said wash liquors into basic copper sulphate by the use of cupric hydroxide derived from the system, allowing the basic copper sulphate to settle out, separating it, heating the liquor and utilizing the same as the water wash liquor in the water washing operation hereinbefore referred to. subjecting the basic copper sulphate to ammonia derived from the system to form tetrammonio copper sulphate and cupric hydroxide, allowing the cupric hydroxide to settle and separating it, utilizing the tetrammonio copper sulphate to form cllulosic spinningsolution and utilizing the ciipric hydroxide to convert more copper sulphate into basic copper sulphate.

9. In the manufacture of cuproammonium rayon, films and the like, a process in which the cellulosic solution is spun into a causic soda setting bath and the filaments are successively subjcted to a water first wash, a dilute acid-wash and a final water wash, which process includes the steps of: utilizing the wash water from the final water wash in preparing the dilute acid wash solution, collecting the used acid wash liquor and freeing it of copper sulphate and substantially all 01' the sulphuric acid and utilizing it for the first water wash, and collecting the used wash liquor from the first water wash and freeing it of copher and ammonia and evaporating water therefrom to increase the concentration of the caustic soda therein, condensing the water evaporated and utilizing it in the final water wash; whereby substantially the same body or water is used over and over again.

WILLIAM H. FURNESS. 

